Elongated articles of various types are commonly covered with foam insulation, which may be pre-foamed or foamed-in-place. For some uses, it is important to sheath the foam from external effects, for example, to prevent absorption of water, deterioration or abrasion. One example is in the insulation of bundles of flexible tubes utilized to conduct liquids such as soda and water from remote refrigerated storage sources to be dispensed at bars. Such bundles of tubing, which must be flexible, sometimes have been bound by spiral wrappings, then insulated with preformed foam insulation, and then covered with an outer spiral wrap. However, such spiral wrapping may not protect reliably, especially because of flexing of the bundle.
Rigid pipes have also been covered with foam sealed by an outer sheathing of plastic film. For example, in U.S. Pat. No. 4,134,782 to Straughan, a foam generator supplies foaming plastic material to the exterior of a pipe which is then covered by a wrapping of plastic film applied in a longitudinal ribbon with an overlapped longitudinal seam. A somewhat similar process is shown in U.S. Pat. No. 3,754,064 to Snelling, in which both the interior and exterior longitudinal sheathing is applied, each with an overlapped longitudinal seam. Likewise, for insulating pipe, spiral wraps of sheathing have been applied, as in U.S. Pat. No. 4,094,715 to Henderson and U.S. Pat. No. 3,941,531 to
While each of these utilizations involves covering an elongated article, a need exists also for providing elongated hollow foam sections, as for ducts to conserve heat energy; and in this instance, both the inner and outer surfaces of such ducts may require sheathings.